Hitherto, there have been already proposed various methods for filling refrigerant of an air conditioner. Then, basic technologies of the refrigerant filling methods and an adequate refrigerant filling amount judging technique will be described below.
As a prior art refrigerant filling method, there has been proposed a method of automatically filling refrigerant by connecting a refrigerant cylinder and a refrigerant circuit via an electromagnetic valve and by automatically opening/closing the electromagnetic valve by judging a refrigerant filling rate from outlet super-cooling degree of a liquid receiver (Patent Document 1 for example).
Furthermore, as the prior art adequate refrigerant filling amount judging method, there has been proposed a method by finding a relationship of indoor and outdoor temperatures of an air conditioner, intake super-heating degree or discharge super-heating degree and a refrigerant filling rate in advance for the machine and storing them (Patent Document 2 for example). There has been also provided a method by finding relational expressions between indoor and outdoor temperatures, intake and discharge super-heating degrees, a refrigerant charging rate and a ratio of length of connected pipes in advance, and calculating the refrigerant charging rate and the ratio of length of connected pipes from measured values of the indoor and outdoor temperatures and calculated values of the intake and discharge super-heating degrees to judge a refrigerant charging amount from the refrigerant charging rate (Patent Document 3 for example). There has been also provided a method by deciding target super-cooling degree from atmospheric temperature and comparing it with super-cooling degree during operation of the refrigerating cycle to fill refrigerant during the time when the super-cooling degree is lower than the target super-cooling degree and to stop filling refrigerant at a point of time when the super-cooling degree coincides with the target super-cooling degree (Patent Document 4 for example).    Patent Document 1: Japanese Patent Application Laid-open No. 2005-114184    Patent Document 2: Japanese Patent Application Laid-open No. Hei. 04-003866    Patent Document 3: Japanese Patent Application Laid-open No. Hei. 04-151475    Patent Document 4: Japanese Patent Application Laid-open No. Hei. 05-099540    Non-Patent Document 1: “Compact Heat Exchanger” by Hiroshi Seshita and Masao Fujii, The Daily Industrial News, 1992    Non-Patent Document 2: “Proc. 5th Int. Heat Transfer Conference” by G. P. Gaspari, 1974